12 R. G. HOSKINS 



the demonstration of the substance as claimed cannot be made with tech- 

 nique at present available. 



Such failure to demonstrate the presence of a specific secretion does 

 not, as a matter of fact, carry much conviction of its absence. In the 

 normal animal a very minute quantity of a given hormone may exercise 

 a cumulative effect extending over days or weeks, thus functioning in a 

 way that could not be detected in a short-lasting experiment. To demon- 

 strate such a cumulative effect would not be practicable ordinarily, be- 

 cause it would necessitate the administration of too great a quantity of 

 foreign blood to an experimental animal, thus introducing an uncon- 

 trollable variable. The obvious method of meeting the difficulty would be 

 to obtain the substance in question from the blood or lymph and then to 

 concentrate it to an extent that would permit its study by the ordinary 

 pharmacologic or animal feeding technique. The evolution of methods 

 for obtaining and concentrating the various undetermined hormones will 

 in all probability await the determination of their chemical properties. 



Many attempts to determine indirectly the presence of essential hor- 

 mones in the blood coming from different endocrin organs have been 

 'iiade. The efferent veins have been ligated and the resulting functional 

 perturbations studied. These manifestations can, with some degree of 

 probability, be regarded as due to deficiencies of the hormones in question. 

 Hartman, for instance, has recently applied this method to the suprarenals. 

 lie found that when the Jumbo-adrenal veins were ligated at the proximal 

 side of the glands sufficient circulation was maintained through collateral 

 vessels to prevent absolute destruction of the glands and the consequent 

 death of the experimental animal. The procedure did result, however, 

 in a number of interesting phenomena. These are to be further studied. 



Perhaps the earliest attempt to utilize the method was made by Gley 

 in 1891. This observer noted that ligation of the pancreatic veins resulted 

 in glycosuria. The experimental animal soon died, however, thus fore- 

 stalling any extensive study of the results of the experiment. Minkowski's 

 well-known experiments on pancreatic extirpation have often been cited as 

 bearing upon the point at issue. If the pancreas be removed in toto the 

 animal soon dies of acute diabetes. But if a portion of the gland be 

 transplanted, preserving the circulation intact but occluding the excretory 

 duct, the animal survives. Forsbach's modification of the experiment 

 may also bo mentioned. The bodies of two dogs were surgically united 

 so as to produce parabiotic "twins." Removal of the pancreas of one 

 resulted in but .slight glycosuria instead of the fatal diabetes which would 

 otherwise have followed. Another variant of the procedure is the crossed 

 circulation experiment of Iledon. This investigator noted that when the 

 blood streams of a diabetic and a normal dog were united by anastomosing 

 an artery and vein of one to a vein and an artery of the other, the gly- 

 cosuria in the diabetic animal was materially reduced. Such experiments, 



